Catalyst Sensor Diagnostics Using Upstream–Downstream Signal Comparison
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Solution Overview
Problem
Existing systems struggle to accurately diagnose malfunctions in three-way catalysts used in emissions control systems of internal combustion engines, which can lead to excessive emissions, necessitating a reliable method to identify faulty sensors.
Innovation Solution
A system that utilizes upstream and downstream air-fuel equivalence ratio sensors to monitor catalyst performance, determining oxygen storage capacity, statistical metrics, and duty cycles to generate fault signals and notifications for stuck sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing diagnostic systems are used to monitor three-way catalysts, then system simplicity is maintained, but measurement precision and reliability of sensor malfunction detection deteriorate
Solution Approach 1:
The diagnostic system is segmented into multiple independent diagnostic routines that evaluate different sensor parameters (oxygen storage capacity, statistical metrics, duty cycle) separately. Each routine processes specific sensor signals independently and generates fault indications that are integrated by the control circuit, allowing complex diagnostics to be broken down into manageable segments that improve detection accuracy without overwhelming system complexity
Solution Approach 2:
The controller acts as an intermediary that receives signals from both upstream and downstream sensors, processes them through multiple diagnostic routines, and generates fault indications. This intermediary processing layer enables precise sensor malfunction detection by comparing and analyzing sensor outputs against expected parameters before generating final diagnostic conclusions
2Reliability
If multiple diagnostic parameters are monitored to improve sensor fault detection, then reliability of emissions control is improved, but device complexity increases
Solution Approach 1:
Multiple diagnostic parameters (oxygen storage capacity measurements, statistical metric comparisons, duty cycle evaluations) are merged into a unified diagnostic system controlled by a single control circuit. The controller integrates signals from upstream and downstream sensors and combines results from different diagnostic routines to generate comprehensive fault indications, improving emissions control reliability while consolidating complexity into a centralized control unit
3Reliability
If continuous monitoring of oxygen storage capacity is performed, then catalyst functionality is maintained, but energy consumption increases
Solution Approach 1:
The system performs continuous monitoring of oxygen storage capacity by continuously processing signals from upstream and downstream sensors through the diagnostic routines. The control circuit continuously evaluates sensor outputs against expected parameters and maintains real-time catalyst functionality assessment, ensuring reliable monitoring while optimizing energy usage through efficient signal processing and comparison operations
Data Source
AI summary
An apparatus includes a processing circuit structured to: receive a first signal indicative of an upstream air-fuel equivalence ratio from a first sensor positioned upstream of an intake of a catalyst; receive a second signal indicative of a downstream air-fuel equivalence ratio from a second sensor positioned downstream of the intake of the catalyst; provide a control signal to an engine to produce a desired first signal; predict an expected second signal based on the desired first signal; compare the first signal to the desired first signal; determine a second signal differential between the second signal and the expected second signal when the first signal is equal to the desired first signal; and, provide a fault signal in response to the second signal differential exceeding a threshold differential. A notification circuit is structured to provide a notification indicating that the second sensor is faulty.